The broad objective of the research proposed herein is to define and validate a method suitable for the analysis of dietary fiber in human foodstuffs and fecal residues. We have been investigating effects of fiber consumption on bowel function in health human subjects under metabolically controlled conditions. Since the composition of the food and the amounts consumed daily were constant, sequential determinations of "digestability" of fiber under these conditions should give accurate measurements of the residue from the specific foods used. A second study designed to evaluate the dietary fiber intake of college students, based on 2-day dietary intake records, is in progress. During these investigations we have found the published methods of fiber analysis to be unsatisfactory. Briefly, they either generate fiber residues contaminated with starch and protein, depend on the use of enzymes contaminated with hemicellulases, or are unnecessarily laborious. Because of the relative simplicity and reproducibility of the neutral detergent fiber (NDF) method and the high quality of experiments upon which it is based, we feel that it has the greatest potential for studies of this type. Our preliminary work suggests that starch and nitrogen-containing contaminants can be removed from the NDF residue by amylase and/or pancreatin pretreatment. Until the chemical nature of the fiber fractions produced by this method is known, the value of data obtained by its use will be limited. We propose to characterize and quantify the carbohydrate (CHO) hydrolyzates of these fractions from a variety of foods by gas-liquid chromatography (GLC). Comparison with measurements on fiber fractions obtained by accepted methods of plant polysaccharide separations will further verify this method. Also, we cannot justify the assumption that the method used to determine food fiber actually measures the same compounds in fecal fiber. Therefore, our second objective is to characterize, again using GLC, the NDF residues obtained from feces already collected under controlled dietary conditions, from human subjects.